Underground storage cavern and method of making same



S. P. WARREN Dec. 18, 1962 UNDERGROUND STORAGE CAVERN AND METHOD OF MAKING SAME Filed Sept. 22, 1958 INVENTOR. SEYMOUR R WARREN ATTORNEY finite States This invention relates to underground storage facilities and is more particularly directed to a novel storage cavern and a method ofconstructing such facilities for the storage of liquid or gaseous fuels and the like.

The use of gaseous or liquid fuels for heating and other purposes remote from the sources thereof is commonplace and various means are used to convey these fuels to regions relatively remote from the source. Where pipe lines are used, the heavy investment in the pipe line facilities requires, from a standpoint of sound economics, that full capacity of the line be used substantially constantly. Inasmuch as fuel demand is many times greater in wintertime than in summertime, it is not economically feasible to build transportation for facilities to satisfy the winter demand and allow the excess capacity to be idle during the summer months. It is therefore a more practical solution to provide storage facilities whereby a smaller transportation capacity can be operated to full capacity all year around and any excess transported during the time of low demand will be stored to supplement that transported during period of high demand.

in view of the vast quantity of fuel to be stored in such reserve facilities, the cost of and area required by the use of above ground tanks and reservoirs is a material factor.

in dealing with this problem in older gas fields, it is a common practice to draw off excess gas from newer and more remote sources and direct it into existing depleted oil and gas wells in order that it may subsequently be withdrawn therefrom as needed. This method often results in losses in that not all the fuel introduced can be recovered. Also it is not always that these depleted wells are available or located in a vicinity where convenient to the place of the fuels.

Furthermore, it has become common to liquefy petro leum gases and the increased production has further increased the problems of providing suitable storage facilities therefor. Due to the high vapor pressure of the liquefied gas, the storage facilities are required to be designed to withstand these pressures, adding substantially to the cost thereof. It has been customary to store these liquefied gases in Water leached caverns in salt formations in abandoned mines and quarries in impermeable shale or limestone formations or in carverns excavated for that purpose. Further, underground concrete storage tanks and buried sections of pipe have been used to a limited extent in such storage. Natural formations and caverns are usually difficult to find in the area where they are needed and even when found they are not always suitable.

Where underground storage has been devloped in salt, shale or limestone formations there is a practical limitation on the maximum size of such caverns and their proximity to the surface. Where caverns have been constructed, elaborate means must be provided to support the roof and sides where the cavern is substantial in size. it has been proposed to provide concrete liners or rooms of diffierent sizes and leave columns throughout the excavation to support the roof and sides.

In accordance with this invention an underground storage system is provided which is capable of storing extremely large quantities of liquid or gaseous fuel at a very small unit cost. Further, the invention provides a ethod of constructing storage facilities which are adaptto a wide range of sites.

It is thus an object of this invention to provide a novel and improved underground storage facility.

It is a further object of the invention to provide a novel method for the construction of man-made storage caverns.

It is another object of the invention to provide a novel underground storage facility wherein the dificulty of selecting a site is minimized.

It is yet another object of the invention to provide an underground storage facility of novel construction and arrangement which is of low cost, as compared to other man-made storage facilities.

It is still another object of the invention to provide an underground storage facility which can be constructed with readily available equipment and material.

Various other objects, advantages and features of this invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing in which the sole FIGURE is a vertical sectional view, partly in elevation, of the preferred underground storage facility of this invention.

Referring to the figure, reference numeral 10 identifies the surface of the earth under which the storage caverns are located. It is to be understood that this disclosure encompasses a plurality of caverns as well depicted by the figure. The most important single feature of the storage facility according to this invention is that a portion of the broken rock is allowed to remain in the cavern as a means providing support for the roof and sides. The cavern may be conveniently formed in any formation determined as suitable by acceptable methods. A shaft 11 is started at surface 10 and sunk to a predetermined depth. At a suitable depth a cross cut or drift 13 is started off of shaft 11 and continued far enough to serve as a working passageway. The drift 13 is sloped slightly upwardly from shaft 11 for the purpose to be explained as the description progresses. At predetermined intervals along drift 13 progressing away from shaft 11 a series of raises 1% are started. A raise 15 centrally located with respect to raises 14 and/or the stope to be formed is put up to serve as a passageway for men and tools during the construction work. Raise 15 is put up through the center of a pillar of rock, is always excavated to a higher point than the back of the stope 21 and is connected. to stopes 16 to either side through working manways 1'7. Working man-ways 17 serve as access and exit passages for the workmen and as a storage cache for hose and tools when the shooting is being done. This is one of many known methods of forming a filled stope.

Working through raises 14 and associated working man-Ways 17, the roof and sides of each cavern or stope is drilled and charged for shooting. The broken rock from the roof and sides falls and is retained by control gates 18 placed in raises 1d started at drift 13.

After each round of holes in the roof of the cavern or stope is drilled, loaded and shot, the top of the broken rock in the filled stope 16 must be lowered to maintain a working surface for the workers. The working space is maintained by drawing off a quantity of broken rock through control gates 18. In addition to drawing off the broken rock, there is a certain amount of fine rock, smaller than one-fourth inch, that can be washed out after each round is shot. Water is applied on top of the broken rock within stopes l6 and the fine rock, indicated at F, along with the Water will flow out of raise l4 and by gravity down drift 13, which is sloped, to a sump S at the bottom of shaft 11. The water and fine rock is then pumped or hoisted to the surface for disposal. This washing will increase the voids without interfering with the supporting action of the broken rock. The excess rock drawn through control gates 18 is also conveyed to the surface by conventional methods. Another round of holes is then drilled, loaded and shot and this process is repeated and the man-ways 17 are allowed to fill up with rock without seals as the rock level in the stope reaches each one in succession. A rock pillar 19, one possible method of bottom support, is allowed to remain between each raise 14 and under the filled stope 16 of a size as determined by the type of rock in the formation.

When the cavern reaches the desired height, the last couple of rounds of holes in the roof are drilled, loaded and shot, without drawing off broken rock through gates 18. This rock will fill the open stope 2t and serve as a support for roof 21. Raise is kept mined out to a point always above the roof'Zi of the cavern and lined with such timber support as necessary to protect the workers. Raise 15 is provided with means by which the workers may reach the working face and a pipeway for air and water lines. An air hoist or elevator may be provided to facilitate ingress and egress from the face and the handling of the necessary mining tools. When the cavern is finished or when convenient at a time prior thereto and the open stopes 20 are completely filled with broken rock, a hole may be drilled into the top of raise 15 and a pipe with suitable valve installed to serve as a gas or liquid inlet and outlet for the storage cavern.

When the cavern is completed and the inlet-outlet installed, all tools, equipment and personnel are removed and drift 13 is sealed off by means of a seal 22. Seal 22 is of a ty'e adapted to withstand the working pressures to be encountered within the storage cavern. A conduit 23 is installed in seal 22 near the floor of drift 13 and provided with a control valve 24 on the shaft side to provide a means for draining any water that may accumulate behind the seal. Shaft 11 can then be used to construct other caverns through other drifts 13a which is shown as just being started.

While the amount of broken rock required to fill the open stope and provide the necessary roof and side support will vary, depending on'the character of the rock and the size of the pieces resulting from blasting, it has been found that in most instances leaving from about 40 percent to about 70 percent of the rock in the cavern produces a storage facility which is structurally sound and at the same time provides maximum utility of the available space. The fuel is stored within the voids between the broken rock and the rock provides a continuous support for the roof and for the walls.

Although the above described embodiment discloses the invention as useful for the storage of liquid and gaseous fuels, it is obvious that the storage facilities are useful for the storage of other types of liquids and gases where large underground storage is desired.

While there has been described what at present is considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention. It is aimed therefore in the appended claims to cover all such changes and modifications which fall within the true spirit and scope of the invention.

What is claimed is:

1. In a method of constructing an underground storage facility suitable for the storage of liquids, gases and the 'ke comprising the steps of sinking a shaft extending from the surface of the earth to a region adjacent the desired location of a storage cavern, cutting a drift from said shaft to a point immediately below the desired cavern location, forming a raise from said drift, opening a stope from said raise by removing rock of random size and :shape as fragments from the roof and sides of said raise, wi hd g the Smaller oc f gments throu h the raise to lower the working level of rock within the stope, repeating the steps of removing rock from the roof of said stope and withdrawing smaller rock fragments through said raise as required to maintain a working level until a substantially rock filled cavern of a near desired capacity is produced, and removing additional rock as fragments from the roof of said stope to completely fill the open stope with rock fragments in edge-to-edge contact and support the roof thereof.

2. A method according to claim 1 wherein the larger rock fragments are retained within the storage cavern to occupy from about 40 percent to about percent of the available volume of the cavern and the balance of the cavern volume is made up of voids between the rock fragments.

3. A method of constructing underground storage facilities for the storage of liquids, gases and the like, comprising the steps of: forming a tunnel located beneath the earths surface, forming at least one raise from the tunnel, opening a stope from the raise by removing rock of random size and shape as fragments from the roof and sides of the raise, selectively withdrawing the fine rock by a washing operation and drawing off a selected quantity of broken rock through the raises to lower the working level of rock within the stope, repeating the steps of removing rock from the roof and sides of said stope and withdrawing the fine rock and portions of the rock fragments through the raise as required to maintain a working level until a substantially rock filled cavern providing the desired percentage void space between the rock fragments as produced, and removing additional rock as fragments from the roof and sides of said stope to completely fill the open stope and provide support for the roof and sides of the cavern.

4. A method of constructing underground storage facilities for the storage of liquids, gases and the like, comprising the steps of forming a raise from atunnel located beneath the earths surface, opening a stope from said raise by removing rock of random size and shape as fragments from the roof and sides of said raise, withdrawing a portion of the rock fragments through the raise to lower the working level of rock within the stope, repeating the steps of removing rock from the roof and sides of said stope and withdrawing portions of rock fragments through said raise as required to maintain a working level until a substantially rock filled cavern of a near desired capacity is produced and removing additional rock as fragments from the roof and sides of said stope to completely fill the open stope with rock fragments in edge to edge contact and provide support for the roof and sides of the cavern, the larger rock fragments being retained within the cavern to occupy from about 40 percent to about 70 percent of the available volume of the cavern and the balance of the cavern volume being made up of voids between the rock fragments.

I References Cited in the file of this patent UNITED STATES PATENTS issue 44). 

